Science Snap (#32): Coral currents

Coral is misunderstood. It may look like a beautiful underwater plant, and for a long time it was thought to be one, but is in fact an invertebrate. The coral structures are colonies made up of individual small polyps. These produce an exoskeleton made up of calcium carbonate, which helps to preserve them in life and also in the fossil record.

Another misunderstanding about corals is that, on the whole, they are passive creatures obtaining their nutrients from the ambient flow of the oceans. Recent research at MIT and the Weismann Institute of Science (WIS) suggests otherwise. They have found that the external cilia (small threadlike appendages similar to those found inside a human lung) of the coral generate eddy currents which draw nutrients to, and potentially waste produce away, from the colonies. Using powerful microscopes and high-speed video equipment they have managed to capture this unexpected behavior on film.

Eddy currents being generated by external cilia of coral. The paths of the tracer particles are colour-coded by fluid velocity. Image courtesy of MIT and the researchers

This research maybe an insight into how these tiny creatures have managed to survive, and thrive, so efficiently in the changing ocean environments as well as allowing scientists to visualize cilia-related processes that occur hidden from view inside organisms.